The present invention relates to steering an aerodynamic vehicle, and more particuarly, the invention relates to the control apparatus for steering such a craft, such as a guided ground-to-air missile.
Propelled aerodynamic vehicles can basically be steered in two ways. One mode of operation involves aerodynamic means, such as rudders, airfoils, elevators, etc.; the other mode involves control of the direction of thrust production. Typical control elements here arepivotable nozzles producing thrust. Duplex nozzles are known for that purpose, and are pivoted to change the direction of the thrust vector. Any asymmetry in thrust production tends to change any existing movement, which feature can be utilized for purposes of steering the vehicle. Other ways of thrust vector control involves jet spoilers.
Aerodynamic control surfaces are not suitable at very low speeds (low dynamical pressure), i.e. during take-off; they loose likewise their effectiveness at very high altitude, i.e. at the upper boundary of the atmosphere, and, of course, in outer space. On the other hand, thrust producing steering elements are always effective whenever the engines run. Thus, one has already proposed to combine both methods of steering in that during take-off or starting, the vehicle is being steered by thrust vector control; and during normal cruising the rudder(s) take over.
Vehicles of the type to which the invention refers can be propelled, for example, by means of duplex nozzles which are powered by a single engine. Twin or duplex nozzles have the advantage over single nozzles that opposite pivoting of the two nozzles permits production of roll moments, uniform pivoting is used for pitch and yaw control depending on the orientation of the axis about which the nozzles pivot. Thus, duplex nozzles can readily be used to produce control moments about all three axes of the craft.
The known control apparatus for the adjustment of aerodynamic control surfaces as well as for pivoting nozzles, include individual control motors for each task. Accordingly, the number of motors needed is quite high, e.g. eight. As far as rudders is concerned, certain devices are known to operate the control surfaces with three motors only.